As color filters used for producing solid-state image sensors or liquid display devices that display a color image, color filters having a red filter layer, a green filter layer and a blue filter layer formed on the same plane of a support such that these layers are adjacent to each other, or color filters having a yellow filter layer, a magenta filter layer and a cyan filter layer, are known. In the present specification, these colored filter layers of each color are also referred to as a color pattern.
In recent years, there has been demand for further improvement in fineness of color filters.
However, since there are problems such as difficulty in improving resolution or occurrence of color irregularity due to coarse pigment particles, the conventional pigment dispersion system is not suitable for applications such as solid-state image sensors in which formation of a micronized pattern is required. In order to address these problems, use of a dye has been proposed (for example, Japanese Patent Application Laid-Open (JP-A) No. 6-75375).
For example, it is known that a red dye is used for a red filter array in color filters (for example, JP-A No. 5-5067).
However, since color patterns formed from a dye exhibit insufficient heat fastness or light fastness, studies have been made regarding color filters using an organic pigment that exhibits excellent heat fastness or light fastness.
Methods of producing color filters using an organic pigment include photolithography in which a process of patterning, in which a composition prepared by dispersing an organic pigment in a photosensitive resin is exposed to light and developed, is repeated for a desired number of times (for example, JP-A No. 1-152449) and printing, such as offset printing or inkjet printing, in which inks containing an organic pigment are used.
As organic pigments for producing color filters, use of organic pigments that exhibit excellent heat fastness or light fastness, such as anthraquinone pigments, diketopyrrolopyrrole pigments, quinacridone pigments, isoindoline pigments, perinone pigments, perylene pigments and condensed azo pigments, have been considered.
In this regard, International Publication No. WO05/052074 proposes a red ink composition for producing a color filter, which composition includes a monoazo compound having a naphthalene ring.
However, there is growing demand for even higher dispersion stability than ever in pigment dispersion compositions and colored curable compositions that include an azo pigment. Further, it has been proved that as the dispersion stability of an azo pigment decreases, heat fastness of the color pattern decreases.
In particular, in pigment dispersion compositions and colored curable compositions used for producing a color filter of solid-state image sensors, stable coating property needs to be maintained, and therefore improvements in dispersion stability and heat fastness are highly desired.